Process for condensing chlorine gas



May 16, 1961 H. SCHMIDT ETAL 2,984,078 PROCESS FOR CONDENSING CHLORINEGAS Filed Sept. 12, 1958 CHLOR/NE CONSUMERS 1 I T T CHLORINE MAIN LINE 9I I RES/DUAL GAS I W I 5 ATMOSPHERE Y ABS OLUTE r 2 & INERTGAS 6 2 v o.coou/ve 5 -50 C 4- |APPARATU5 CONDENSER 2.5m ---l STORAGE TANK T Lieu/0CHLOR/NE INVENTORS HEINZ SCHMIDT PAUL RE/NSHAGE/V WALDEMAR ZIEMER FRANZHOLZl/VGER 2,984,078 I l PROCESS FOR CONDENSING CHLORINE GAS HeinzSchmidt, Paul Reinshagen, Waldemar Ziemer, and Franz Holzinger, all ofFrankfurt am Main, Germany, assignors to Farbwerke HoechstAktiengesellschaft vormals Meister Lucius & Bruning, Frankfurt amGermany, a corporation of Germany Filed Sept. 12, 1958, Ser. No. 760,538Claims priority, application Germany Sept. 14, 1957 3 Claims. (Cl. 62-9)The present invention relates to a process for condensing chlorine gas.

. Chlorine condensers often have the function of buffering installationswhich, together with various electrolytic chlorine discharge devices,balance the produc tion and consumption of chlorine so that a constantpres sure is maintained in the chlorine distributing pipe system.

Low temperature cooling apparatus when subjected to stronger loadvariation cannot fulfill the aforesaid buffering function in asufficiently elastic manner, since the condenser spaces are filled withresidual gas and do not permit an instantaneous increase or reduction ofthe condensation capacity without a variation of the gas pressure beinginvolved. The amount of gas that undergoes condensation is oftenregulated by means of shutofi devices which, however, because of thenecessary pressure gradient, cannot be installed without a disadvantagebeing involved, especially into installations which are operated onlyunder a slight superatmospheric pressure.

The object of this invention is to overcome the above difliculties bymeans of an adjustable inert gas cushion which regulates the admissionof chlorine to the cooling surfaces of the condenser.

The process .for condensing chlorine gas according to this inventioncomprises varying the amount of condensing chlorine at a constantcondensation pressure and temperature by means of an inert gas cushionproduced by introducing or withdrawing inert gas.

As inert gases there may be used all gases uncondensable under theconditions prevailing in the chlorine condensation, such as nitrogen,air, gaseous carbonic acid and the noble gases, for example argon. Whenit is desired to produce especially pure gaseous chlorine, it isadvantageous to use nitrogen as inert gas.

According to a modification of the above process the admission or theremoval of inert gas is regulated automatically by the pressureprevailing in the chlorine supply pipe so that the pressure remainsconstant.

The process may also be modified so that the temperature at which thechlorine undergoes condensation is automatically kept constant. In thecase where a multiple stage apparatus is concerned, the inert gas may beadmitted in the first stage while it is withdrawn in the last stage.

In using the process of this invention in industry uncondensable dryinert gas is injected into the condenser to reduce the condensationcapacity, the amount of inert gas injected being controlledautomatically by the pressure prevailing in the chlorine distributingpipe. In case it is necessary to increase the condensation capacity, thepartial pressure of the inert gas is reduced by means of a blow-throughvalve that opens automatically, whereby a portion of the inert gas addedand the residual condensing chlorine gas are caused to flow off. It isaccordingly possible to increase or reduce the amount of condensingsubstance within reasonable time by means of an automatic regulator at aconstant pressure of chlotime and at a constant condensationtemperature. When a multiple stage process is concerned, the inert gasis advantageously injected in the first stage, that is when the chlorineundergoes condensation, while the inert gas is withdrawn in the secondor last stage of the process. A better understanding of the inventioncan be had by reference to the accompanying drawing, which showsschematically the process and apparatus of the invention. Chlorineobtained by electrolysis or chlorine of other origin of 98.8% purity andcontaining altogether 1.2% of uncondensable gases, such as nitrogen, iscompressed to 2.5 atmospheres absolute and transported to a series ofchlorine consumers by means of a conduit system 1. To maintain thepressure prevailing in this system of conduits at'a constantlevel, thelatter are connected by shunt conduit means 2 with condenser 3, whosecooling surfaces are kept at a constant temperature of 30 C.

by cooling apparatus 4 employing a boiling cooling agent, for exampledifluoromonochloromethane. The cooling capacity of condenser 3 andcooling apparatus 4 are so dimensioned that in the extreme case thetotal amount of chlorine produced can be liquefied; in the chosenexample, which is carried out under a pressure of 2.5 atmospheresabsolute at a temperature of 30 C. and where the chlorine contains 1.2%of uncondensable gases, about 99% of the chlorine can be condensed. Bymeans of automatically controlled valve 5, in communication withcondenser 3, the amount and partial pressure of the gases withincondenser 3 is controllable so that the desired degree of liquefactionis reached and the pressure in the system is kept constant at 2.5atmospheres absolute. At equilibrium, the equilibrium partial pressureof chlorine in condenser 3 is 1.2 atmospheres. Since the system is undera total pressure of 2.5 atmospheres, the partial pressure ofnon-condensable gases is 1.3 atmospheres, and the partial volumes ofchlorine and non-condensable gas are 48% and 52%. If consumer demand forchlorine drawn from conduit 1 decreases, tending to increase thechlorine pressure in conduit 1, pressure regulated control means 7activate circuit 10 opening valve 5, which permits escape of theequilibrium gas mixture from condenser 3. The system will tend toreestablish equilibrium conditions by condensation of chlorine gas andsimultaneous accumulation of non-condensable gases within condenser 3.Thus, the pressure stress in conduit 1 is relieved by condensation ofchlorine.

Conversely, if consumer demand tends to decrease the chlorine supply,valve 5 is closed, partially or completely, to discourage escape of theequilibrium gas mixture and to throttle further condensation of chlorinein condenser 3. However, if large variations in the chlorine demandoccur, the time lag involved in building up the content ofnon-condensable gas in the condenser'to the value found for the gas inthe equilibrium gas mixture is too lengthy to permit effective control,since only small amounts of non-condensable gas are normally found inthe chlorine and are introduced into the condenser in this manner.However, according to the invention, chlorine can be quickly displacedfrom the condenser surfaces by increasing the partial pressure ofnoncondensable gases in the condenser by another means, and the processof condensation thus quickly throttled. This is done by supplying anamount of dry uncondensable gases to the condenser 3; the amount ofinert gas supplied is controlled by a valve 6 which receives itsimpulses through circuit '9 from a pressure meter 7 inserted in thechlorine supply pipe. By means of valve 6 the amount of uncondensableinert gas is increased as the pressure falls in the chlorine supply pipeor reduced as the pressure increases; in the extreme case the valve isclosed. When this valve is opened, valve 5 in communication withcondenser 3 is simultaneously closed,

Patented lVlay 16, 19 61 31 and reversely. Valve. 5 in communication=-with. condenser 3 has the function of maintaining the pressure in thechlorine supply lines at a constant level by regulating the amount ofthe escaping -cushion of inert gas.

Dilution ofchlorine in conduit 1 by'inert gas introcluced into condenser3 through fvalve 6zis prevented: by check valve 8 in shunt conduit means2.

We claim:

1. In a method'for distributing gaseous chlorine'at a substantiallyconstant pressure fronr achlorine source to achlorine sinlethrough adistributing system comprising, in communication, saidsource,-saidlinkrand a condenser in which chlorine in eXcessof thatrequired to maintain said substantially'constant pressure is condensedat a substantially constant'condensation' temperature and pressure, theimprovement" which comprises rapidly decreasing-the amount of chlorinecondensed in saidcondenser when chlorine demand at said sink is isincreased, and rapidly. increasing'the amount" of chlo-' rine condensedin-said condenser when chlorine'demand at said sink islow by withdrawingthe gaseous contents 4 of said condenser, including chlorine and inertgas; whereby the partial pressure of inert gas in the condenser isdecreased.

2. A method according to claim 1 wherein the admission and withdrawal ofinertgas from said condenser are-regulated automatically by the pressureof chlorine gas in the distributing system exterior to said condenser.

3; A method according to claim 1 wherein, in'a distributing systemcomprising a'chlorine source and sink and a plurality of condensingstages, inert gas is introduced into the first of said stages andwithdrawn from the last of said stages.

References Cited in the file of this patent UNITED STATES PATENTS KogelJuly 2, 1957 OTHER REFERENCES Chemical'Engineers Handbook (Perry);published" by McGraw-Hill (New York), third edition 1950 (Text bookEdition); pages 290 and 291 relied on.

